C Program Design C Arrays 主講人：虞台文. Content Basics Defining Arrays Array Initialization...

C Program DesignC Arrays

主講人：虞台文

Content Basics Defining Arrays Array Initialization Static Arrays Passing Arrays to Functions Array Examples

– Find Minimum and Maximum– Bubble Sort– Binary Search

Strings and String Functions Multi-dimensional Arrays

Basics

陣列 (Arrays)

Array is a data structure that stores contiguous data elements of the same type.

Examples:int score[50];char address[50];double distance[50];

address

distance

陣列 (Arrays)Examples:int score[50];char address[50];double distance[50];

address

distance

score[0]

score[1]

score[49]

陣列 (Arrays)

address

distance

address[0]address[1]address[2]

address[49]

陣列 (Arrays)

address

distance ...

distance[0]

distance[49]

陣列之使用Examples:int score[50];char address[50];double distance[50];

Array elements are like normal variablesscore[ 0 ] = 90;

printf( "%d", score[ 0 ] );

Perform operations in subscript. – If x equals 3

c[ 5 - 2 ] c[ 3 ] c[ x ]

陣列使用注意事項陣列之索引 (index) 由 0開始

– 一陣列若含 n元素，其索引由 0至 n-1

C Compiler 對陣列索引不做 out of range 檢查– 易產生程式錯誤，甚或系統失敗– 寫程式時程式設計師應保證陣列索引不超出範圍

Defining Arrays

arrayType arrayName[numberOfElements];

Examples:

int c[10];

float myArray[3284];

int c[10];

float myArray[3284];

Defining Multiple Arrays of Same Type

arrayType arrayName[numberOfElements];

Examples:

int age[10], score[50];

double distance[50], average[100];

int age[10], score[50];

double distance[50], average[100];

Array Initialization

Initializers

int n1[10]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

int n2[10]={1, 2, 3, 4, 5};

int n3[10]={0};

int n4[10];

int n5[]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

int n1[10]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

int n2[10]={1, 2, 3, 4, 5};

int n3[10]={0};

int n4[10];

int n5[]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

範例： Initializers

#include <stdio.h>

main(){ int n1[10]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; // all elements are initialized int n2[10]={1, 2, 3, 4, 5}; // rightmost elements become 0 int n3[10]={0}; // rightmost elements become 0 int n4[10]; // defined an array of size 10; don’t guess their values int n5[]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; // initializer detetermines the size int i;

for(i = 0; i<10; i++) printf("n1[%d]=%2d n2[%d]=%2d n3[%d]=%2d n4[%d]=%2d n5[%d]=%2d\n", i, n1[i], i, n2[i], i, n3[i], i, n4[i], i, n5[i]); }

#include <stdio.h>

Debug Mode

#include <stdio.h>

Release Mode

對未定義初值之陣列元素值勿做臆測對未定義初值之陣列元素值勿做臆測

Static Arrays

Automatic Arrays

#include <stdio.h>

Automatic arrays are created and, hence, initialized each time the corresponding function is called.Making arrays static “may” resolve the problem.

範例：

繪製一檔案中各字母（不區分大小寫）出現頻率之直方圖繪製一檔案中各字母（不區分大小寫）出現頻率之直方圖

// histogram.c#include <ctype.h>

#define FALSE 0#define TRUE (!FALSE)

#define HTG_SUBMIT_CHAR 0#define HTG_GET_CHAR_FREQ 1#define HTG_GET_TOTAL 2

int histogram(int action, int c){ static int first = TRUE; // enter first time static int freq['z' - 'a' + 1], total=0;

if(first){ // initialization needed int i; for(i = 0 ; i <'z'-'a' + 1; i++) freq[i]=0; first = FALSE; // initialized }

switch(action){ case HTG_SUBMIT_CHAR: if(!isalpha(c)) return 0; total++; return ++freq[toupper(c) - 'A']; case HTG_GET_CHAR_FREQ: if(!isalpha(c)) return 0; return freq[toupper(c) - 'A']; default: return total; }}

// histogram.h#define HTG_SUBMIT_CHAR 0#define HTG_GET_CHAR_FREQ 1#define HTG_GET_TOTAL 2

int histogram(int action, int c);

範例：

繪製一檔案中各字母（不區分大小寫）出現頻率之直方圖繪製一檔案中各字母（不區分大小寫）出現頻率之直方圖

int histogram(int);

How about if static is missing?

範例：繪製一檔案中各字母（不區分大小寫）出現頻率之直方圖繪製一檔案中各字母（不區分大小寫）出現頻率之直方圖

// main.c#include <stdio.h>#include "histogram.h"

main(){ int c, total, i;

do{ c = getchar(); histogram(HTG_SUBMIT_CHAR, c); } while(c != EOF);

total = histogram(HTG_GET_TOTAL); if(total==0) return 0;

for(i = 0; i < 26; i++){ int stars, j; printf("%c ", i+'A'); stars = 200.0 * histogram(HTG_GET_CHAR_FREQ, i+'A') / total; for(j=0; j<stars; j++) putchar('*'); putchar('\n'); } return 0;}

Passing Arrays to

Functions

Passing Arrays to Functions

To pass an array argument to a function, specify the name of the array without any brackets

Array size usually passed to function, e.g.,int myArray[ 24 ];

myFunction( myArray, 24 ); In C, array’s name denotes the starting address (reference)

of the array Hence, the above function call is equivalent to

myFunction( &myArray[0], 24 ); Modifying the array element in the function, the original ele

ment is modified

Passing Arrays to Functions

Passing the array’s reference to functions makes sense for performance reasons

– Remark: call this as call-by-reference is, in fact, improper since this is not done by compiler

If arrays were passed by value, a copy of each element would be passed. For large, frequently passed arrays, this would be time consuming and would consume considerable storage for the copies of the arrays.

Function Prototypes with Arrays

void myFunction( int array[], int arraySize );

void myFunction( int[], int );

範例#include <stdio.h>

void listElements(int[], int);void RemoveFactor5(int[], int);

main(){ int data[]={12, 55, 6, 21, 35, 90, 91};

printf("Original elements in data[] are: \n"); listElements(data, sizeof(data)/sizeof(int));

RemoveFactor5(data, sizeof(data)/sizeof(int));

printf("\n\nRemoving factor 5, elements in data[] become:\n"); listElements(data, sizeof(data)/sizeof(int)); printf("\n");}

void listElements(int vals[], int size){ int i;

for(i=0; i<size; i++) printf("%d ", vals[i]);}

void RemoveFactor5(int vals[], int size){ int i;

for(i=0; i<size; i++) while(vals[i] % 5 == 0 && vals[i] > 0) vals[i] /= 5;}

#include <stdio.h>

main(){ int data[]={12, 55, 6, 21, 35, 90, 91};

將一正整數陣列中之各元素移除因子 5

範例#include <stdio.h>

main(){ int data[]={12, 55, 6, 21, 35, 90, 91};

#include <stdio.h>

main(){ int data[]={12, 55, 6, 21, 35, 90, 91};

將一正整數陣列中之各元素移除因子 5

Array Examples

範例：// MinMax.c#include <stdio.h>#include <limits.h>

#define MAX_NUM_ELEMENTS 50

int ReadData(int[], int);

main(){ int data[MAX_NUM_ELEMENTS]; int i, count; int min = INT_MAX, max = INT_MIN;

count = ReadData(data, MAX_NUM_ELEMENTS);

for(i = 0; i < count; i++){ if(min > data[i]) min = data[i]; if(max < data[i]) max = data[i]; }

printf("min=%d and max=%d\n", min, max);}

int ReadData(int data[], int size){ int count=0;

while(count < size && scanf("%d", &data[count]) != EOF) count++;

return count;}

// MinMax.c#include <stdio.h>#include <limits.h>

return count;}

搜尋最大值與最小值搜尋最大值與最小值

範例：// MinMax.c#include <stdio.h>#include <limits.h>

return count;}

// MinMax.c#include <stdio.h>#include <limits.h>

return count;}

搜尋最大值與最小值搜尋最大值與最小值

Bubble Sort

void BubbleSort(int data[], int n)

int tmp, i, j;

for(i=0; i<n-1; i++)

for(j=0; j<n-i-1; j++)

if(data[j] > data[j+1]){

tmp = data[j];

data[j] = data[j+1];

data[j+1] = tmp;

int tmp, i, j;

for(i=0; i<n-1; i++)

for(j=0; j<n-i-1; j++)

tmp = data[j];

data[j+1] = tmp;

範例 : Bubble Sort (I)

int tmp, i, j;

for(i=0; i<n-1; i++)

for(j=0; j<n-i-1; j++)

tmp = data[j];

data[j+1] = tmp;

int tmp, i, j;

for(i=0; i<n-1; i++)

for(j=0; j<n-i-1; j++)

tmp = data[j];

data[j+1] = tmp;

int tmp, i, j, sorted;

for(i=0, sorted=FALSE; !sorted && i<n-1; i++)

for(j=0, sorted=TRUE; j<n-i-1; j++)

tmp = data[j];

data[j+1] = tmp;

sorted = FALSE;

int tmp, i, j, sorted;

for(i=0, sorted=FALSE; !sorted && i<n-1; i++)

for(j=0, sorted=TRUE; j<n-i-1; j++)

tmp = data[j];

data[j+1] = tmp;

sorted = FALSE;

範例 : Bubble Sort (II)

Binary Search

int binSearch(int x, int v[], int n);

125125

137137

140140

180180

201201

400400

012345678910

binSearch(137, v, 11)

Binary Search

high =

low <= high

mid = (low + high) / 2 = 5

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 125 > 25

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 125 > 25

high =high = mid - 1

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 9 < 25

high =

low <= high

mid = (low + high) / 2 = 2

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 9 < 25

high =

low = mid + 1

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

high =mid =

v[mid] = 25 == 25

low <= high

mid = (low + high) / 2 = 3

Binary Search

high =

low <= high

mid = (low + high) / 2 = 5

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 125 > 25

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 125 > 45

high =high = mid - 1

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 9 < 45

high =

low <= high

mid = (low + high) / 2 = 2

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

v[mid] = 9 < 45

high =

low = mid + 1

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

high =mid =

v[mid] = 25 < 45

low <= high

mid = (low + high) / 2 = 3

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

high =mid =

v[mid] = 25 < 45

low = mid + 1

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

high =

v[mid] = 80 > 45

low <= high

mid = (low + high) / 2 = 4

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

high =

v[mid] = 80 > 45

high = mid - 1

Binary Search

125125

137137

140140

180180

201201

400400

012345678910

high =

low <= high

範例 : Binary Search/* binsearch: find x in v[0] <= v[1] <= ... <= v[n-1] */int binSearch(int x, const int v[], int n){ int low, high, mid;

low = 0; high = n - 1; while (low <= high) { mid = (low+high)/2; if (x < v[mid]) high = mid - 1; else if (x > v[mid]) low = mid + 1; else /* found match */ return mid; } return -1; /* no match */}

/* binsearch: find x in v[0] <= v[1] <= ... <= v[n-1] */int binSearch(int x, const int v[], int n){ int low, high, mid;

low = 0; high = n - 1; while (low <= high) { mid = (low+high)/2; if (x < v[mid]) high = mid - 1; else if (x > v[mid]) low = mid + 1; else /* found match */ return mid; } return -1; /* no match */}

範例 : Binary Search

Strings and

String Functions

Strings in C Null-terminated string In C, a string is a character array t

erminated with a '\0' to mark the end.

char str[]="hello\n";

Example: h (68)

e (65)

l (6C)

o (6F)

\n (0A)

\0 (00)

str str[0]

str[1]

str[2]

str[3]

str[4]

str[5]

str[6]

sizeof(str) = 7

char str[]={'h', 'e', 'l', 'l', 'o', '\n', '\0'};

Reading Strings

char string[BUF_SIZE]; // ensure buffer large enough

scanf("%s", string); // not &string

scanf("%s", &string[0]);

Reads characters until white character encountered.

Be careful not to write past end of array, as it is possible to do so.

範例： Reading Strings#include <stdio.h>

main(){ char string1[ 20 ]; /* reserves 20 characters */ char string2[] = "string literal"; /* reserves 15 characters */ int i; /* counter */

/* read string from user into array string1 */ printf( "Enter a string: " ); scanf( "%s", string1 ); /* input ended by whitespace character */

/* output string1 and string2 */ printf( "string1 is: %s\nstring2 is: %s\n", string1, string2 );

/* output space separated string for string1 */ printf( "string1 with spaces between characters is:\n" ); for ( i = 0; string1[ i ] != '\0'; i++ ) printf( "%c ", string1[ i ] );

printf( "\n" );}

#include <stdio.h>

printf( "\n" );}

範例： Reading Strings#include <stdio.h>

printf( "\n" );}

#include <stdio.h>

printf( "\n" );}

atoi and itoa

int atoi( const char[] ); // ascii to integer

int itoa( int, char[] ); // integer to ascii

char str[]="10759";int val;

val = atoi(str);

str '1'

'9''\0'

1075910 = 2A071600

char str[]="10759";int val;

val = atoi(str);

str '1'

'9''\0'

1075910 = 2A071600

Byte order: Big-Endian & Little-Endian

char str[6];int val=10759;int len;

len=itoa(val, str);

1075910 = 2A071600

'9''\0'

// >> 5

範例 :atoi

/* atoi: convert decimal string s to integer */

int atoi(const char s[])

int i=0, val=0, sign;

sign = s[i] == '-' ? -1 : 1; /* record sign */

if(s[i] == '+' || s[i] == '-') i++; /* skip sign if existent */

while(s[i] >= '0' && s[i] <= '9') /* non-numeric terminated */

val = 10 * val + (s[i++] - '0');

return val * sign;

/* atoi: convert decimal string s to integer */

int atoi(const char s[])

int i=0, val=0, sign;

sign = s[i] == '-' ? -1 : 1; /* record sign */

if(s[i] == '+' || s[i] == '-') i++; /* skip sign if existent */

while(s[i] >= '0' && s[i] <= '9') /* non-numeric terminated */

val = 10 * val + (s[i++] - '0');

return val * sign;

範例 :itoa/* itoa: convert n to characters in s and return length */int itoa(int n, char s[]){ int i, negative; n = (negative = (n < 0)) ? –n : n; /* record sign */

/* make n positive */ i = 0; do { /* generate digits in reverse order */ s[i++] = n % 10 + '0'; /* get next digit */ } while ((n /= 10) > 0); /* delete it */ if (negative) s[i++] = '-'; s[i] = '\0'; reverse(s); return i;}

/* itoa: convert n to characters in s and return length */int itoa(int n, char s[]){ int i, negative; n = (negative = (n < 0)) ? –n : n; /* record sign */

/* make n positive */ i = 0; do { /* generate digits in reverse order */ s[i++] = n % 10 + '0'; /* get next digit */ } while ((n /= 10) > 0); /* delete it */ if (negative) s[i++] = '-'; s[i] = '\0'; reverse(s); return i;}

範例 :strlen, reverse/* strlen: return the string length of s */int strlen(const char s[]){ int i=0; while(s[i]) i++; return i;}

/* reverse: reverse sting s */void reverse(char s[]){ int i, j, temp;

i = 0; j = strlen(s) - 1;

while(i < j){ temp = s[i]; s[i] = s[j]; s[j] = temp; i++; j--; }}

/* strlen: return the string length of s */int strlen(const char s[]){ int i=0; while(s[i]) i++; return i;}

/* reverse: reverse sting s */void reverse(char s[]){ int i, j, temp;

i = 0; j = strlen(s) - 1;

while(i < j){ temp = s[i]; s[i] = s[j]; s[j] = temp; i++; j--; }}

範例 :atoi(recurive version)

// RecursiveAtoi.c

// recursive_atoi: convert a decimal string (str) from index (start)// into an integer with heading value (val)int recursive_atoi(const char str[], int val, int start){ if(str[start] == '-') return -recursive_atoi(str, val, start+1); else if(str[start] == '+') return recursive_atoi(str, val, start+1); else if(str[start]=='\0') return val; else return recursive_atoi(str, val * 10 + (str[start] - '0'), start+1);}

// atoi: convert a decimal string str into an integer// assume str is error freeint atoi(const char str[]){ return recursive_atoi(str, 0, 0);}

// RecursiveAtoi.c

start=3

'1' '2' '5' '9' '3' '0' '1' '9' '\0'str

val=125

// RecursiveAtoi.c

start=0

'1' '2' '5' '9' '3' '0' '1' '9' '\0'str

// RecursiveAtoi.c

start=8

'1' '2' '5' '9' '3' '0' '1' '9' '\0'str

val=12593019 answer

// RecursiveAtoi.c

// recursive_atoi: convert a decimal string (str) from index (start)// into an integer with heading value (val)int recursive_atoi(const char str[], int val, int start){ if(str[start] == '-') return -recursive_atoi(str, val, start+1); else if(str[start] == '+') return recursive_atoi(str, val, start+1); if(str[start]=='\0') return val; else return recursive_atoi(str, val * 10 + (str[start] - '0'), start+1);}

// RecursiveAtoi.c

// recursive_atoi: convert a decimal string (str) from index (start)// into an integer with heading value (val)int recursive_atoi(const char str[], int val, int start){ if(str[start] == '-') return -recursive_atoi(str, val, start+1); else if(str[start] == '+') return recursive_atoi(str, val, start+1); if(str[start]=='\0') return val; else return recursive_atoi(str, val * 10 + (str[start] - '0'), start+1);}

start=8start=8

'1' '2' '5' '9' '3' '0' '1' '9' '\0'str

val=12593019 answer

start=3start=3

'1' '2' '5' '9' '3' '0' '1' '9' '\0'str '1' '2' '5' '9' '3' '0' '1' '9' '\0'str

val=125

// RecursiveAtoi.c

// main.c#include <stdio.h>

int atoi(char[]);

main(){ char str[20]; printf("Enter a numeric string:"); scanf("%s", str);

printf("The value you type is:%d\n", atoi(str));}

// main.c#include <stdio.h>

int atoi(char[]);

main(){ char str[20]; printf("Enter a numeric string:"); scanf("%s", str);

printf("The value you type is:%d\n", atoi(str));}

範例 :itoa(recurive version)

// RecursiveItoa.c

// recursive_itoa: itoa之輔助函式// 將 n值轉為十進制字串，將結果從 s矩陣之 start處開始擺放// 傳回值為轉換後之字串長度int recursive_itoa(int n, char s[], int start){ int len = 0; if(n/10) len = recursive_itoa(n/10, s, start); s[start+len] = n % 10 + '0'; return len+1;}

// itoa: convert integer (n) into string (s) and return lengthint itoa(int n, char s[]){ int i=0; if(n<0){ s[i++]='-'; n = -n; } i += recursive_itoa(n, s, i); s[i]='\0'; return i;}

// RecursiveItoa.c

x x x x x x x x xs

// RecursiveItoa.c

x x x x x x x x xs n=1024‘1’ ‘0’ ‘2’ ‘4’

Return 4

// RecursiveItoa.c

x x x x x x x x xs

// RecursiveItoa.c

String Functions

<stdlib.h>

<string.h>

Multi-dimensional

Arrays

Two-Dimensional Arrays

A collection of a fixed number of components arranged in two dimensions– all components are of the same type– also called matrices

Syntax:dataType arrayName[intexp1][intexp2];

where intexp1 and intexp2 are expressions yielding positive integer values

範例 :#define MONTHS 12#define YEARS 5

int main(void){ float rainFall[YEARS][MONTHS]; int i, j;

for ( i = 0; i < YEARS; i++ ) { for ( j = 0; j < MONTHS; j++ ) { printf( "Rain fall for year %d, month %d: ", i, j ); scanf( "%f", &rainFall[i][j] ); } } // . . .}

#define MONTHS 12#define YEARS 5

int main(void){ float rainFall[YEARS][MONTHS]; int i, j;

for ( i = 0; i < YEARS; i++ ) { for ( j = 0; j < MONTHS; j++ ) { printf( "Rain fall for year %d, month %d: ", i, j ); scanf( "%f", &rainFall[i][j] ); } } // . . .}

2D-Arrays in Memory

#define YEARS 5#define MONTHS 12

float rainFall[YEARS][MONTHS];

rainFall[0][0]rainFall[0][0]

. . .. . .

Logical View

Physical ViewrainFall[0]

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall,

rainFall[0]

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall

2D-Arrays in Memory

. . .. . .

Logical View

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall,

rainFall[0]

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall

sizeof(rainFall)=?sizeof(rainFall)=?

sizeof(rainFall[i])=

?, i=0, …, 4

sizeof(rainFall[i])=

?, i=0, …, 4sizeof(rai

nFall[i][j])=?, i=0,

…, 4, j=0, …, 11

sizeof(rainFall[i][j

])=?, i=0, …, 4, j=0

, …, 11

2D-Arrays in Memory

. . .. . .

Logical View

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall,

rainFall[0]

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall

C compiler doesn’t perform out-of-bound

checking. C compiler doesn’t perform out-of-bound

checking.

Accessing, e.g., rainFall[0][14] is not invalid. Accessing, e.g., rainFall[0][14] is not invalid.

2D-Arrays in Memory

. . .. . .

Logical View

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall,

rainFall[0]

rainFall[1]

rainFall[2]

rainFall[3]

rainFall[4]

rainFall

Can you figure out, though improper, the

addresses of rainfall[5], rainfall[6], …

Can you figure out, though improper, the

addresses of rainfall[5], rainfall[6], …

? How?

MONTHS

MONTHS 12

2D-Array Initialization

#include <stdio.h>

main(){ int array1[2][3] = {{1, 2, 3}, {4, 5, 6}}; int array2[2][3] = {{1, 2, 3}, {4}}; int array3[2][3] = {{1, 2, 3}};

int array4[][3] = {1, 2, 3, 4, 5, 6}; int array5[][3] = {1, 2, 3, 4}; int array6[][3] = {1, 2, 3};

int array7[][3] = {{1, 2}, {4}}; int array8[][3] = {1, 2}; int array9[][3] = {1};

printf("Size of array1 to array9 are:\n" "%d %d %d %d %d %d %d %d %d\n", sizeof(array1), sizeof(array2), sizeof(array3), sizeof(array4), sizeof(array5), sizeof(array6), sizeof(array7), sizeof(array8), sizeof(array9));}

#include <stdio.h>

printf("Size of array1 to array9 are:\n" "%d %d %d %d %d %d %d %d %d\n", sizeof(array1), sizeof(array2), sizeof(array3), sizeof(array4), sizeof(array5), sizeof(array6), sizeof(array7), sizeof(array8), sizeof(array9));}

2D-Array as Function’s Argument

#include <stdio.h>

void listElements(char heading[], int array[2][3]){ int i, j;

printf(heading);

for(i=0; i<2; i++) for(j=0; j<3; j++) printf("%d ", array[i][j]);

printf("\n"); }

#include <stdio.h>

printf(heading);

printf("\n"); }

#include <stdio.h>

printf(heading);

printf("\n"); }

#include <stdio.h>

printf(heading);

printf("\n"); }

Provide no information to the compiler for locating array’s

elements.

Provide no information to the compiler for locating array’s

elements.

#include <stdio.h>

printf(heading);

printf("\n"); }

#include <stdio.h>

printf(heading);

printf("\n"); }

void listElements(char heading[], int array[][3])

#include <stdio.h>

void listElements(char heading[], int array[][3]){ int i, j;

printf(heading);

printf("\n"); }

#include <stdio.h>

void listElements(char heading[], int array[][3]){ int i, j;

printf(heading);

printf("\n"); }

#include <stdio.h>

void listElements(char[], int[][3]);

printf("Size of array1 to array9 are:\n" "%d %d %d %d %d %d %d %d %d\n", sizeof(array1), sizeof(array2), sizeof(array3), sizeof(array4), sizeof(array5), sizeof(array6), sizeof(array7), sizeof(array8), sizeof(array9) );

listElements("array1: ", array1); listElements("array2: ", array2); listElements("array3: ", array3); listElements("array4: ", array4); listElements("array5: ", array5); listElements("array6: ", array6); listElements("array7: ", array7); listElements("array8: ", array8); listElements("array9: ", array9);}

#include <stdio.h>

void listElements(char[], int[][3]);

printf("Size of array1 to array9 are:\n" "%d %d %d %d %d %d %d %d %d\n", sizeof(array1), sizeof(array2), sizeof(array3), sizeof(array4), sizeof(array5), sizeof(array6), sizeof(array7), sizeof(array8), sizeof(array9) );

listElements("array1: ", array1); listElements("array2: ", array2); listElements("array3: ", array3); listElements("array4: ", array4); listElements("array5: ", array5); listElements("array6: ", array6); listElements("array7: ", array7); listElements("array8: ", array8); listElements("array9: ", array9);}

Multidimensional Arrays

A collection of a fixed number of components arranged in n ( 1) dimensions– all components are of the same type– also called n-dimensional arrays

Syntax:dataType arrayName[intexp1][intexp2]…[intexpn];

where intexp1, intexp2, … are expressions yielding positive integer values

範例 :#define YEARS 5#define TOTALSALES 10#define PRODUCTS 5

int main(void){ int sales[YEARS][TOTALSALES][PRODUCTS]; int i, j, k;

for ( i = 0; i < YEARS; i++ ) for ( j = 0; j < TOTALSALES; j++ ) for ( k = 0; k < PRODUCTS; k++ ) { printf("In year %d, the number of items sold by "sales %d for product is", i, j, k); scanf( "%d", &sales[i][j][k] ); } // . . .}

#define YEARS 5#define TOTALSALES 10#define PRODUCTS 5

int main(void){ int sales[YEARS][TOTALSALES][PRODUCTS]; int i, j, k;

for ( i = 0; i < YEARS; i++ ) for ( j = 0; j < TOTALSALES; j++ ) for ( k = 0; k < PRODUCTS; k++ ) { printf("In year %d, the number of items sold by "sales %d for product is", i, j, k); scanf( "%d", &sales[i][j][k] ); } // . . .}

N-Dim Array as Function’s Argument

When declaring a multi-dimensional array as a formal parameter in a function– can omit size of first dimension but not other

dimensions– there is no check if the array indices are within

bounds

Passing an array to the function by writing its name. – An array’s name represents its address (reference)

練習 :1. Write a C program which output an NN magic

square, where N is an odd integer. An NN magic square has N2 cells that are filled with integers from 1 to N2 , and all of its column sums, row sums and the two diagonal sums have the same value.

Reference:

練習 :Knight’s Tour

2. Problem 6.19 of the textbook3. Problem 6.20 of the textbook

C Program Design C Arrays 主講人：虞台文. Content Basics Defining Arrays Array Initialization...

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